Reversible refrigerating system and control therefor



Sept. 7, 1965 w. o. LUM 3,204,420

REVERSIBLE REFRIGERATING SYSTEM AND CONTROL THEREFOR Original Filed Nov. 29, 1955 3 Sheets-Sheet 1 L k *1: I/ 1 "1 2E 6 34 35 45 47 II 67 'IO 65 INVENTOR. Walter 0. L um ATTORN EYS Se t. 7, 1965 w. o. LUM 3,204,420

REVERSIBLE REFRIGERATING SYSTEM AND CONTROL THEREFOR Original Filed Nov. 29, 1955 3 Sheets-Sheet 3 INVENTVOR.

Wa I te r O. L u m WMTQM ATTORNEYS United States Patent 3,204,420 REVERSIBLE REFRIGERATING SYSTEM AND CONTROL THEREFOR Walter 0. Lum, 228 NE. Hernando Ave., Port Charlotte, Fla.

Continuation of abandoned application Ser. No. 549,705, Nov. 29, 1955. This application Sept. 6, 1962, Ser. No. 221,915

17 Claims. (Cl. 62-160) This is a continuation of application Serial No. 549,705, filed November 29, 1955, now abandoned.

This invention relates to refrigerating systems and particularly to such systems of the compressor-condenserexpander type which may be reversed to provide reverse cycle operation.

In recent years substantial applications have been found for reverse cycle refrigerating systems which are commonly called heat pumps; these systems are frequently made to be reversible so that they may be employed for cooling in the summer as Well as for heating in the winter. It is highly desirable, especially in the case of the smaller heat pumps for residential installations, that the reversing of the system be accomplished easily and preferably that it be elfected under automatic control. The reversing of a heat pump circuit requires that the functions of the heat exchange units be interchanged, the heating unit becoming the cooling unit and vice versa. In installations where reversing is accomplished by reversing the paths of the refrigerant in a compressor type refrig crating system an arrangement of selecting valves must be provided in the refrigerant lines. Some form of unloading device is commonly provided in order to equalize the refrigerant pressures on the high and low sides of the system to prevent starting of the compressor under load and also to facilitate the operation of the reversing valves. The various types of controls provided heretofore for the purpose of reversing heat pumps have afforded satisfactory operation for many applications; however, many of the controls are complicated in construction or require separate unloading devices or place limitations on the location and arrangement of the components of the refrigerating system, and they have not proved entirely satisfactory for the wide range of present day applications of the heat pump. Accordingly it is an object of the present invention to provide a reversible refrigerating system including an improved control for affording a rapid and ellicient reversing operation.

It is another object of this invention to provide a refrigerating system of the compressor-condenser-expander type including an improved arrangement of valves to secure quick and eflicient reversing of the refrigerant circuit of the system.

It is another object of this invention to provide an improved automatic reversing valve for refrigerating systems.

It is a further object of this invention to provide an improved two-way check valve for reversible refrigerating systems.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification,

Briefly, in carrying out the objects of this invention in one embodiment, a closed cycle refrigeration system is provided which includes two heat transfer units or coils arranged to act alternatively as evaporators and condensers in the refrigerating circuit. A fiow restricting element which separates the high and low pressure sides of the system, and may be a so-called capillary tube, is connected between the two heat transfer coils, and the other 3,204,420 Patented Sept. 7, 1965 ends of the coils are connected in a refrigerant circuit including the compressor and are arranged with branch circuits so that the direction of flow from the compressor to the coils may be reversed. The exhaust or discharge port of the compressor is connected to both the ends of the coils remote from the capillary tube and the suction or inlet port is similarly connected. Valves are provided in the branches of the conduits leading from the compressor ports to the coils so that the reversing action may be accomplished by the automatic operation of the valves. One of the branch lines is provided with a two-way check valve which operates automatically to complete the required connection to the coil not selected for connection to the other port of the compressor. The other branch lines leading from the other port of the compressor are provided with two independent valves which are controlled alternatively so that either one or the other is opened to determine the direction of circulation of the refrigerant through the heat transfer coils. The two check valve elements of the two-way check valves are constructed so that they are interlocked and close their respective conduits alternatively. These check valves are further constructed to minimize vibration or chattering during their operation. The independently controlled valves are automatic in operation, the selection of one valve or the other for operation being accomplished by opening a corresponding pilot valve Which provides communication between a control chamber in the valve and the outlet side of the valve in order to release pressure in the control chamber. When one of the pilot valves is open the main valve piston automatically moves to its open position and, so long as there is fluid flow, remains there until the pilot valve is again closed. Upon closing of a pilot valve the main valve closes depending upon a flow of fluid to the control chamber through a bleed port connected to the inlet side of the main valve. With the pilot valve either open or closed the valve opens when the opposite valve has been selected for operation so that a passage is provided between the two sides of the system and thereby allows the pressure on the two sides to be equalized. This arrangement for unloading upon a change over from one valve control to the other is particularly useful for quick change over operations such as may occur when the system is reversed for defrosting purposes.

For a better understanding of the invention reference may be had to the accompanying drawings in which:

FIG. 1 is a schematic diagram of a reversible refrigerating system embodying the invention;

FIG. 2 is an enlarged sectional view of a two-way check valve employed in the system of FIG.1;

FIG. 3 is an enlarged sectional view of one of the solenoid control valves employed in the system of FIG. 1.

FIG 4 is a schematic diagram of a reversible refrigerating system similar to that of FIG. 1 illustrating another embodiment of the invention;

FIG. 5 is an enlarged sectional view of the two-way check valve employed in FIG. 4;

FIG. 6 is a diagrammatic illustration of a portion of a system similar to that of FIG. 4 provided with a modified control arrangement for the independent valves; and

FIG. 7 is .an enlarged sectional view of a portion of a valve similar to that of FIG. 3 illustrating another embodiment of the invention.

Referring now to the drawing, the reversible refrigeration system shown in FIG. 1 comprises two heat transfer coils 10 and 11 connected in a closed refrigerant circuit with an electric motor driven compressor 12. The adja cent ends of the coils 10 and 11 are connected by a suitable expansion valve or differential pressure device illustrated by way of example as a flow restrictor or capillary tube 13 and the other ends of the coils 10 and 11 are condissipated by the fluid flowing over the coil 11.

nected to conduits 14 and 15 and may either receive or discharge refrigerant through these conduits depending upon the positions of two alternatively actuated mechanically independent control valves 16 and 17 and a two-way check valve 18. The two-way check valve 18 is connected to receive hot compressed refrigerant from the discharge port of the compressor 12 through a discharge line 20 and to direct the discharged refrigerant either to the conduit 14 through a branch conduit 21 or to the conduit 15 through a branch conduit 22. The direction of circulation of the refrigerant depends upon the positions of the valves 16 and 17 which are in branch conduits 23 and 24, respectively, connected to the intake of the compressor and have their inlet ports connected to conduits 14 and 15. When the valve 16 is open, as shown refrigerant thus flows to the coil 11 where it is cooled and condensed by air or other fluid circulated over the coil 11 and is liquefied. The liquefied refrigerant flows to the coil 10 through the restrictor 13 land is vaporized by the absorption of heat from the air or other fluid flowing over the surface of the coil 10, the vaporized refrigerant being withdrawn through the conduit 14 by operation of the compressor. In this posit-ion of the control, heat is absorbed from the air in the room to be conditioned and is discharged to the outside where it is In the present embodiment both the coils 10 and 11 have been illustrated as refrigerant to air heat exchangers, the coil 10 picking up heat directly from air in the enclosure and the coil 11 discharging heat to outside air circulated over its surfaces.

In order to reverse the direction of flow of refrigerant in the system, the positions of the valves 16 and 17 are reversed, valve 17 being opened and the valve 16 closed; when this change in position of the valves is effected and the compressor 12 is operating, the two-way valve 18 moves to its right hand position because of the change in direction of fluid flow and differential pressures and the hot compressed refrigerant is discharged through the left hand port of the valve 18 and flows tothe coil 10 where it is cooled by the air circulated overv the coil and is liquefied; this supplies heat to the air in the enclosure to be conditioned and increases its temperature. The refrigerant liquefied in the coil 10 flows through the capillary tube 13 to the coil 11 where it is vaporized by the absorption of heat from the outside air, the vaporized refrigerant being returned to the compressor through conduit 15, open valve 17 and branch conduit 24.

The valves 16 and 17 are operated alternatively by energization of solenoid coils 25 and 26, respectively. The electrical control circuit for effecting energization of either of the coils 25 and 26 includes a thermostatic switch 27, indicated diagrammatically as a bi-metallic strip, which is positioned to be responsive to the temperature of the air in the room to be conditioned. Operation of the thermostatic switch controls the energization of a cooling control 30 and a heating control 31 alternatively; the controls 30 and 31 are arranged to determine the position of a snap-acting selector switch 33 connected to energize the coil 25 when it is in its right-hand position and the coil 26 when it is in its left-hand position. Energy for actuation of the controls 30 and 31 is provided by a transformer 34 connected across two sides of the three phase supply lines 35. When the bi-metal element 27 moves to the left upon a demand for cooling and lies in the dotted line position indicated in the drawing a circuit is closed to a coil 36 of the control 30; this circuit may be traced from the left hand side of the secondary of the transformer 34 through a normally closed defrosting control switch 37, the thermostatic blade 27, the coil 36 and thence back to the secondary of the transformer 34 through a connection 38 and a return lead 39. When '4 the coil 36 is thus energized an armature 40 of the relay 30 is moved to its upper position and a switch blade 41 thereon engages its stationary contacts to connect a supply line 42 to a line 43 and thence to a connection 44 and a coil 45 back to the center one of the power leads 35. This energizes the coil 45 and closes a three phase switch 46 to connect the supply lines 35 to motor leads 47 and thereby energizes the motor of the compressor 12. Raising of the armature 41) of the control 30 also rotates a rocker bar 48 of the selector switch 33 clockwise about its central fixed pivot to its upper position as shown in the drawing in the event it is not already in that position. When the rocker 48 is rotated to the position shown on the drawing a spring 49 connected between the pivoted switch blade of the selector 33, indicated at 50, and an upward extension 51 on the rocker bar 48 snaps the blade to its right hand position as shown on the drawing to energize the coil 25 of the valve 16. The circuit for the coil 25 may be traced from the lowermost power lead 35 to the line 42, thence through the switch blade 50, a line 53, the coil 25 and a connection 54 back to the center one of the power leads 35. When the temperature in the room to be conditioned falls below a predetermined value the bi-metal blade 27 moves to the right and engages a contact 55 to connect a coil 56 of the control 31 across the secondary of the transformer 34. Upon energization of the coil 56, an armature 57 of the control 31 is raised until its blade, indicated at 58, engages its fixed contacts and connects the coil 45 of the motor switch 46 across the line in the same manner as closing of the switch 41, the contacts of the control 31 being connected to the lines 42 and 44 by branch connections 66 and 61. Movement of the armature 57 to its upper position reverses the position of the rocker bar 48 of the selector switch 33, a lug62 on the lower end of the armature 57 engaging the right hand end of the rocker bar and rotating the bar counterclockwise to move the upright member 51 to the left causing the spring 49 to move over center with respect to the fixed pivot of the switch blade 50 so that the switch blade snaps to its left hand position and connects the coil 26 across lines 35 to open the valve 17. The circuit for the coil 26 may be traced from the lower power lead 35 to the line 42 and thence through the switch blade 50 and a line 63 to the coil 26 and back to the center one of the lines 35 through the line 54. It will be noted that only one of the coils 36 and 56 of the controls 30 and 31 may be energized at a time, the position of the blade 27 determining which of these coils is to be energized. When the coil 36 is de-energized and the armature 40 falls it opens the circuit of the coil 45 and disconnects the motor thereby stopping the compressor. The compressor is thus stopped during the period when the bi-metallic element 27 is moving away from its left hand contact and before it engages the right hand contact. In addition to these controls, however, there is provided a de-frosting control 65 which is connected through a link 66 to the normally closed switch 37. Upon a demand for defrosting which may occur, for example, when the outdoor coil 11 has become coated with frost during winter operation, the control 65 operates to move the switch 37 to open its right hand contact and to engage is left hand contact, indicated at 67, and thereby disconnect the bimetal element 27 and connect the coil 36 directly in circuit with the secondary of the transformer 34. This is the position for the cooling operation and on energization of the coil 36 the compressor 12 continues to run and the valve 16 is opened so that the valves are in the position shown in the drawing and hot compressed refrig erant is discharged into coil 11 thereby melting the frost collected on the surface of the coil. After the defrosting operation has been completed the control 65 will return the switch 37 to its normal position thereby restoring control to the thermostatic element 27. It will thus be seen that on operation of the defrosting control there may be a quick change from operation of the compressor to supply refrigerant to one coil to operation to supply refrigerant to the other coil and that there will not be a sufiicient period for unloading of the system through the capillary tube during this changeover. Equalization of pressure is accomplished however because the valves 16 and 17 are constructed so that either valve whether its pilot 115 is open or closed will open automatically when the other valve is selected for operation and will thus provide direct communication between the high and low pressure sides of the system thereby unloading the system Whether or not the compressor is running. This feature insures quick and etficient reversing of the refrigerating system and prevents starting the compressor under load.

The manner in which the valves 16, 17 and 18 are constructed and arranged and the manner in which they function to control the operation of the refrigerating system will be more readily understood on reference to FIGS. 2 and 3 which illustrate the details of construction of these valves.

The construction of the valve 18 is shown in FIG. 2. The valve is symmetrical about its longitudinal axis and the two check valve members are of identical construction; for purposes of illustration, the left-hand check valve has been shown in full and the right-hand check valve in section. The valve comprises a cylindrical body 70 closed by end plates 71 and 72 through which the outlet connections 21 and 22 communicate with the interior of the valve. Partition members 73 and 74 near the ends of the body 70 divide the interior of the cylinder into a central intake chamber 75 and two end or outlet chambers. Valve discs 76 and 77 are provided to close the ports in the partition 73 and 74, indicated at 78 and 79, respectively. These valve discs are mounted on reduced end portions of a carrying yoke or tie bar 80. As illustrated by the construction of the valve disc 77 and its assembly, the disc comprises a cup-like member seated against a shoulder 81 formed at the end of the bar 80 and fitting about the reduced end portion 82 of the bar. A valve gasket or seal 83 of suitable packing material is secured within the cup member by a sleeve or washer 84 which fiits over the reduced portion 82 and is secured rigidly in position by a nut or cap 85 threaded onto a further reduced portion 86 of the bar 80. The bar 80 and the valve discs are held in spaced relationship within the cylinder 70 by a pair of four-armed spiders 87 and 88, the ends of the arms being bent at right angles and arranged to slide on the inner wall of the cylinder 70 longitudinally thereof; the spiders are held apart by a compression spring 90. The spiders 87 and 88 are mounted on sleeves 91 and 92 which are slidable on the bar 80 and have their inner ends slightly spaced to afford movement with respect to one another. The clearance of the sleeves on the arms may be of the order of one or two ten-thousandths of an inch; with such clearance a layer of oil exists between the sleeve and the bar 80 during normal operation due to the oil always present in the refrigerating system. This film of oil provides a damping action which retards relative movement of the valve stem and spiders and minimizes chattering of the valves in response to the pulsations of the compressor. The spring 90 presses the spiders 87 and 88 outwardly against the valve discs which are fixed on the bar 80 and in this position the arms of the spider extend longitudinally beyond the disc surface and as the valve assembly moves toward one of the ends or partitions 73 and 74 the arms of the spider engage the partition before the valve disc comes into engagement with the valve seat formed about the ports 78 and 79. In FIG. 2, the valve disc 77 is shown in position in engagement with the seat in the partition member 74 and the spider 88 is in engagement with the partition near the outer periphery thereof. In this position the spider 88 has been pressed away from engagement with the disc 77 which has been forced by the difference in pressure between the inlet 20 and outlet 22 into engagement with the outlet port. It will thus be apparent that when the pressure is reduced the t 6 spring will again force the spiders 87 and 88 apart and will thus move the disc 77 away from the valve seat. This assures opening of the valve on reduction in the pressure differential and facilitates the shifting of the valve upon the reversing of the refrigerant circuit.

During the operation of the valve shown in FIG. 2, assuming that the system has been operating with the valve closed in its right-hand position as illustrated, the disc 77 being in engagement with the valve seat about the port 79, then when it is desired to reverse the system the solenoid 26 is de-energized and the solenoid 25 is energized. This causes the valve 16 to open and because the valve 17 remains open so long as reverse flow continues,the high and low sides of the system are equalized and the pressure difference between the two sides of the disc 77 is reduced so that the spring 90 forces the valve 77 open. As soon as the valve 16 closes, the pressure differential will be built up by operation of the compressor and the valve assembly of the check valve 18 will move to the left because of the high pressure in the central chamber 75 as compared with the pressure in the conduit 21 which is connected to the inlet of the compressor. This will force the valve disc 76 against the seat about the port 78 and the system will then be completely reversed and will operate to supply hot compressed refrigerant through the port 79 and conduit 22 to the transfer coil 11 and to withdraw cold vapor through the conduit 14 and back to the inlet of the compressor. It is thus apparent that the two-way check valve 18 which comprises the interconnected valve members 76 and 77 provides a simple and effective arrangement for cooperation with the alternatively operable valves 16 and 17 for quickly and efliciently reversing the circuit of the refrigerating system.

The details of construction of the valves 16 and 17 are identical and for purposes of illustration the valve 16 is shown in FIG. 3. The valve 16 comprises a cylindrical body portion 95, which may be a section of seamless tubing, and is provided with end caps 96 and 97 which are soldered, Welded or otherwise suitably secured to the two ends of the body 95. The outlet conduit 23 extends upwardly into the body through an opening in the lower end cap 96 and terminates above the midportion of the body. The valve seat 98 is secured on the inner end of the tube 23 and a piston valve 100 is mounted within the cylinder 95 and is movable between a lower position in engagement with the valve seat 98 and an upper position in which it engages a stop ring 101 formed in the upper end cap 97. The inlet connection 14 enters the side of the cylinder 95 between the end cap 96 and the upper end of the outlet 23; thus the piston valve 100 divides the cylinder 95 into a lower chamber 102 and an upper chamber 103. The lower chamber 102 constitutes a flow chamber and when the valve is open, fluid flows from the inlet 14 about the outside of the tube 23 and thence through the opening at the upper end of the tube and then out through the tube. The position of the piston valve 100 depends upon the differential pressure conditions between the two chambers and the upper chamber 103 serves as the regulating or control chamber of the valve. The piston 100 is preferably biased downwardly into its position against the valve seat 98 by three equally spaced springs 104, one of which is shown on the drawing. The valve piston 100 comprises a main body portion 105 and a central control valve section 106. During the assembly of the piston the section 106 is inserted from the lower side after a valve packing or gasket 107 has been inserted within a central opening 108 in the disc 105. The section 106 is pressed into position until a flange 110 engages and presses a packing ring 107 into position whereupon the upper edges of the section 106 are peened over at 111 to secure the section-s securely and permanently within the main valve body 105. A relief orifice 112 is provided in the disc 105 above the packing ring 107 which is in communication with an annular groove 113 and acts to provide pressure relief on the upper side of the valve disc. A central valve port 114 is provided in the section 106 and is arranged to be closed by a pilot valve 115, the lower conical end of which engages and closes a central passage formed in a valve seat or insert 116 and which constitutes a continuation of the valve port 114. The lower end of section 106 is provided with a boss r sleeve 117 having a larger internal diameter than the port 114 and having openings 118 in the side thereof to provide communication between the port 114 and the outlet connection 23. The form of the boss 117 provides a venturi effect reducing the pressure drop during flow of fluid through the main valve and also inducing low pressure in the control chamber when the pilot valve is open. In order to prevent reverse flow of fluid through the port 114, a valve disc 120 is provided within the sleeve 117 and is held in place by a washer 121 secured within the sleeve 117 by bending over the lower end of the sleeve as indicated at 122. When there is a reverse pressure in the system and fluid tends to flow upwardly through the port 114, the disc 120- rises until it strikes the body 106 at the lower end of the port and prevents the passage of fluid through the port. This prevents quick closing of the piston valve upon a reversal of the pressure conditions.

When the valve pin 115 is in engagement with the seat 116 and the port 114 is closed, the fluid under pressure from the inlet reaches the control chamber 103 through a bleed port 123 extending through the body 105 of the valve piston. The size of the bleed passage is determined by the size of the hole drilled in the disc 105 less the size of a wire restrictor and cleaner member 124 which is inserted in the bleed passage 123 and has its ends turned over to limit its longitudinal displacement. The pin 124, however, is sufliciently loose that its movement serves to keep the bleed passage open at all times. The pin 124 as illustrated has its lower end bent at right angles but extending substantially tangentially of the cylinder.

In order to actuate the piston valve 100 when it is in its closed position, the solenoid coil 25 is energized and lifts an armature 125 upwardly within a tube 126 until the shoulder of the plug 127 in the lower end of the armature engages a head 128 on the pin 115 and snaps the valve pin from its seat thereby opening the port 114. As soon as the valve port 114 is opened, fluid under pressure within the regulating chamber 103 flows downwardly to the outlet connection 23 and the pressure within the chamber 103 falls to a value nearly that within the outlet 23. Any pressure difference between the chamber 103 and the outlet 23 after the pilot valve has opened is due to the flow of fluid through the bleed orifice 123 and thence through the chamber 103 to the port 114. This difference in pressure is in effect negligible so that the pressure on the annulus of the valve piston 100 about the valve seat 98 quickly lifts the piston away from the valve seat when the pressure is released by opening of the pilot valve, the piston moving upwardly in opposition to the force of the three springs 104.

The tube 126 is sealed into the upper enclosure 97 and has at its upper end a non-magnetic closure plug 130 which completes the closed housing of the valve body. The armature 125 is slidable within the tube 126 and the head 128 of the valve 115 slides freely within a cylindrical recess 131 within the armature 125, this being the recess closed by the plug 127. It will thus be apparent that the armature 125 must move a sutficient distance to bring the top of the plug 127 into engagement with the lower shoulder of the head 128 of the valve before the valve is moved by the armature. By allowing the armature to move first and engage the plug after initial movement, a snap action is provided and this quickly overcomes the pressure difierence acting on the valve 115. The coil 25 is mounted within a housing 132 which fits about the tube 127 and rests on the end plate 97 of the valve body. The housing 132 is securely held in position against the valve body by a friction lock fastener 133.

Under transient conditions during the reversing operation the pressure relationship may be reversed so that a higher pressure exists in the outlet conduit 23 than in the inlet chamber 102; the passage of the high pressure fluid through the port 114 is then prevented by closing of the check valve disc 120. Under these conditions, a lower pressure prevails in the control chamber 103 than in the outlet 23, and the piston valve is forced away from the seat 98 by the difference in pressure. In order to prevent valve closing forces resulting from low pressure due to radial flow at a critical velocity which would hold the valve nearly closed upon the initial unseating of the valve, the main body of the valve is provided with a depending annular flange 134 extending about the valve seat 98 and spaced slightly with respect thereto to provide an axially directed annular path between the side wall of the seat 98 and the flange. The low pressure due to the high velocity flow through this passage does not provide an axial component of force tending to draw the piston valve 100 against the top of the seat 98. This prevents the locking of the piston near the valve seat 98 and allows the valve to move to its fully open position.

During the normal operation of the valve 16, when the valve has been opened and the coil 25 is de-energized, the armature 125 falls and quickly seats the pilot valve to close the port 114. Fluid now begins flowing back into the chamber 103 through the bleed orifice 123. The rate of flow depends upon the size of the bleed orifice. Valve 16 remains open so long as reverse gas flow continues after closing of the pilot valve; it is this action which delays closing of the valve and provides an open passage between the two sides of the refrigerating system through the valves 16 and 17 when one of the valves is de-energized and the other valve energized and thus affords quick reversal with the compressor running.

It will be observed that the mechanical construction of the valve 16 is simple and rugged, the valve body 95 and the outlet connection 93 being concentric lengths of tubing and the end caps 96 and 97 easily machined circular plates. In addition, the non-magnetic tube 126 is also a length of tubing concentric with the main body 95 and is easily secured in the upper cap 97. The valve is extremely simple in operation and requires no external operating members with fluid seals and in addition it is not necessary for the solenoid valve to have any mechanical connection between the valve piston and the armature of the solenoid, the entire operation of the piston being accomplished by opening and closing of the pilot valve and the resulting change in differential pressure.

One of the advantages of the refrigeration system as shown in FIG. 1 is that the two-way check valve 18 is arranged in the path of the hot compressed refrigerant and can therefore be of a smaller size than a similar valve arranged in the low pressure side of the system, the compressed refrigerant on the high side having a much smaller volume than the low side refrigerant. The valves 16 and 17 which are arranged on the low pressure side of the system and are actuated by the solenoid coils 25 and 26 are in the path of the cool, vaporized refrigerant returning to the compressor. The cooling capacity of the re turning refrigerant is thus available in the valves 16 and 17 to carry heat away from the coils 25 and 26. One other advantage of the system wherein the solenoid valves 16 and 17 are located in the suction line of the compressor is that, in the event the energization for the solenoids 25 and 26 should fail, the valves 16 and 17 will close and overloading of the compressor will thereby be avoided.

The three valves 16, 17 and 18 are physically separate and may be located in any position where the required refrigerant circuit connections can be made, the control of the system being coordinated by the alternative operation of the solenoids. Thus this invention provides a system which is extremely flexible and permits a wide range of different installation arrangements.

The arrangement of the solenoid valves and the twoway check valve may be interchanged in the system, the solenoid valves being placed in the compressor discharge line and the two-way check valve in the suction line. This interchanged arrangement of the valves may be desirable in some installations and in FIG. 4 there is illustrated diagrammatically a system in which the valves are so interchanged. The components of the system and of the electrical control circuit are essentially the same as those of the system shown in FIG. 1 and corresponding parts have been designated by the same numerals with the sufiix letter a. The system differs from that of FIG. 1 in that the solenoid valves are arranged in the discharge connection of the compressor 12a as indicated at 136 and 137 and the two-way check valve is arranged in the suction line of the compressor as indicated at 138. The solenoid valve 136 is actuated by a solenoid coil 140 and the valve 137 by a solenoid coil 141.

During the operation of the system shown in FIG. 4,

when there is a demand for cooling, the bi-metallic element 27a moves to the left to engage its left-hand contact and energizes the coil 36a, thereby closing the switch 41a and starting the compressor by closing of the power switch 46a. The circuit for the solenoid coil 141 is energized through the line 42a, the switch blade 50a in its right-hand position, a line 142, the coil 141 and the return line 5411. This energizes the solenoid coil 141 and opens the valve 137, as indicated on the drawing, whereupon refrigerant is discharged through the valve 137 and flows to the outdoor heat transfer coil 11a. Here the refrigerant is cooled and liquefied and then flows through the capillary tube 13a to the indoor heat trans fer coil 10a where it is vaporized by the absorption of heat from the air within the enclosure to be conditioned, the vaporized refrigerant being returned to the compressor through the left-hand port of the valve 138 and a suction line 143. Upon a change in the temperature conditions in the zone being conditioned and a movement of the bi-metal element 27a to the right to engage contact 55a, the coil 56a is energized; the armature 57a is then lifted to shift the position of the control switch 33a by rocking the member 48a counterclockwise about its position and also closing the switch 58a to start the motor. Engagement of the switch 33a with its left-hand contact closes a circuit in the line 42a through a lead 144 to the coil 140, thereby opening the valve 136. The valve 137 now closes, its solenoid coil 141 having been de-energized by operation of the switch 33a, and there is a pressure equalizing connection between the two sides of the system through the two valves 136 and 137 in the same manner as in the operation of the valves 16 and 17 of FIG. 1. Hot compressed refrigerant is now supplied to'the indoor heat transfer coil 10a through the valve 136 and the valve 138 shifts to the right. The liquefied refrigerant flows through the capillary 13a to the heat transfer coil 11a where it is vaporized by the absorption of heat from the outdoor air and is returned to the compressor through the right-hand port of the twoway valve 138.

In the event that during the operation of the heat transfer coil 10a as a heating coil in the manner just described, the coil 11a becomes coated with a layer of frost of sufiicient thickness the defrosting control 65a will perate to shift the switch 37a to its left-hand position in engagement with its contact 67a and will thereby switch the control from the coil 56a to the coil 36a and reverse the system, de-energizing the coil 140 and energizing the coil 141 so that the positions of the valves 136 and 137 are reversed. During this operation, the open passage through the valves 136 and 137 will afford unloading of the compressor by equalizing the pressure on the two sides of the system before the valve 136 has closed.

It will thus be seen that the operation of the system of FIG. 4 is essentially the same as that of FIG. 1. The valve 138 for use in the suction line of the compressor is of a different construction from that of the valve 18 in that the check valves must operate in the opposite directions from the directions of the valve 18. The structural details of the valve 138 are shown in FIG. 5. AS shown in this figure the valve 138 comprises a cylindrical body 146 divided into a central chamber 147 and then chambers 148 and 149 by two partition members 150 and 151 in which are formed the valve ports 152 and 153. The partition members 150 and 151 are secured in spaced relationship within the cylinder 146 by cylindrical spacing members 155, 156 and 157, and the entire assembly is held together by end plates 158 and 159. The inlet connections 23a and 24a are soldered, welded or otherwise suitably secured in openings in the end plates 158 and 159, respectively. The valve assembly comprises two valve discs, 161 and 162, mounted on a valve stem or bar 163 and arranged in the chambers 148 and 149 to close the valve ports 152 and 153 upon movement from the respective chambers toward the central chamber 147. Upon a change in the pressure differentials in the system, the one of the valves 161 and 162 closes which is on the side of the system connected to the higher pressure coil. In FIG. 5 the valve 161 is shown closed. The valve assembly including the stem 163 and the valves 161 and 162 is held in position and guided in its movement in the cylinder 146 by a pair of spiders 164 and 165 which are urged toward the valves 161 and 162, respectively, by springs 166 and 167. The springs 166 and 167 are retained betwen the spiders and the ends of the valve stem 163 by flanged washers 168 and 169 which are secured to the stem 163 near the ends thereof. The function of the spiders 164 and 165 is essentially the same as that of the guide spiders in the modification of FIG. 2, and, as shown in FIG. 5, the bent arms of the spider 164 which engage the internal wall of the sleeve 155 are in engagement with the partition member 150 near the end thereof and the spring 166 is under compression. Thus, whenever the pressure differential between the inlet and the outlet of the valve 161 is relieved, the spring 166 will act to move the valve 161 away from its seat on the partition member 150.

In order to prevent chattering due to the pulsations of the compressor, a clamping device is provided which comprises a Weight 170 :slidably mounted on the central portion of the valve stem 163. The clearance between the weight and the valve stem is of the same order as that of the spider sleeves on the valve stem of FIG. 2 and thus any tendency of the valve stem to move will provide a damping action due to the film of oil between the weight and the stem and the inertia effect of the weight. It will readily be apparent from FIGS. 4 and 5 that whenever the solenoid valves 136 and 137 are shifted to direct highpressure refrigerant to a different end of the valve 138, the valve will quicl'cly close and is positive in action. This valve 138 thus provides the same function of operating automatically depending upon the operation of the solenoid valves as does the valve 18 in the modification of FIG. 1. Both valves provide positive automatic operation depending upon the positions of the main control valves which are operated alternatively by the solenoid controls.

In FIG. 6 there .is illustrated a modified arrangement for controlling the operation of the main alternatively operated valves whether they be connected in the high pressure line or in the suction line. In this modified construction, instead of providing a pilot valve in the piston valve assembly, the pilot valve is connected externally of the control valve. In the modification of FIG. 6, the two valves have been shown arranged in the suction line of the compressor. The two valves indicated at 173 and 174 are constructed in essentially the same manner as the valve shown in FIG. 3 except that the pilot valve port 114 and the pilot valve assembly are omitted and instead the end caps, indicated at 175 and 176, are provided with stop rings 177 and 178 for limiting the upward movement of the pistons indicated at 180 and 181, respectively. The control chamber of the valve 173, indicated at 182, is connected to the suction line 183 through the lefthand port of a ilot valve control 184 and a pilot connection 185 which is in direct communication with the suction line 183. This connection thus operates in the same manner as the pilot valve port 114 of FIG. 3. The pilot valve control 184 comprises a left-hand valve 186 and a right-hand valve 187, connected by a common stern 188 and actuated by a pivoted lever 189 upon operation of a control bar 190. The control bar 190 is biased to its left-hand position by a spring 191 and is moved to its right-hand position by a solenoid coil 192. The valve 173 corresponds to the valve 16 in FIG. 1 and when this valve is open the system is operating to cool the air within the room to be conditioned, the coil operating as the evaporator of the refrigeration system. The electrical control to be employed with the valve system of FIG. 6 is essentially the same as that for the control of the system in FIG. 1, the chief difference being that instead of employing the back contacts of the switch 50 and the lead line 63 for energizing the solenoid 26 of FIG. 1, it is unnecessary to provide a solenoid control because the spring 191 returns the pilot valve control to its position with the right-hand valve 187 open. In the position shown in FIG. 6, it is assumed that the valve assembly is connected in the system of FIG. 1 and that the coil 192 is connected in the same position in the circuit as the coil 25 and is energized. When the pilot valve 184 is in its left-hand position and is open from the conduit 185 through the valve 186 to the control chamber 182, the valve piston 180 moves to its upper position as shown in the drawing; refrigerant then is withdrawn from the indoor coil through a conduit 194 and is returned to the compressor suction line 183 through the valve 173 and a connection 195.

When the coil 192 is de-energized and the pilot valve assembly 184 reversed, the valve 186 is seated and the valve 187 moves away from its seat to provide communication between the suction line and the control chamber of the valve 174, indicated at 196. The valve 174 then opens, provided the refrigeration system is in operation and the compressor running, and the system is reversed in the same manner as is effected in the operation of the system of FIG. 1, when the control is transferred from the valve 16 to the valve 17. It will be noted that the entire control assembly 184 of the pilot valve is arranged in a closed casing 198 so that it is a part of the refrigerant circuit, the leads for the coil 192 being suitably sealed against gas leakage.

In FIG. 7 there is shown a modified form of the solenoid-actuated valve of the same general type as that of FIG. 3. In this valve an arrangement is provided for positively displacing the actuating valve piston after opening of the pilot valve; valves of this type may be found desirable under some conditions of operation, and the construction of the piston is somewhat simplified in that a skirt such as, that indicated at 134 in FIG. 3

'is not necessary. The solenoid is arranged to lift the valve away from the seat and thereby avoids the radial flow velocity pressure effect present when the piston is free-floating and is urged toward the valve seat by the springs 104 indicated in FIG. 3. The valve illus trated in FIG. 7 comprises an outer cylindrical casing 200 having an inlet connection 201 and an outlet connection 202 at the top of which is arranged the valve seat 203.

The piston valve indicated at 204 is seated on the upper end of the outlet 202 in its lowermost position as illustrated and is provided with a bleed passage 205 corresponding to the bleed passage 123 of FIG. 3. A port 206 is provided in the center of the piston 204 and corresponds to the port 114 of FIG. 3, it being closed by a needle valve 207 which is slidably mounted in an upstanding cylindrical sleeve or base 208 attached to the piston 204. Pilot valve 207 is actuated by an armature 210 which is moved upwardly upon energization of its solenoid (not shown). A pair of spaced extensions 211 and 212 extend downwardly from the armature 210 on either side of the boss 208 and short of the upper surface of the piston 204. Cross bars 213 and 214 are provided between the extensions 211 and 212 and are positioned to engage the valve 207 and the piston boss 208, respectively. When the armature 210 moves upwardly, it travels a short distance until the bar 213 engages a head 215 on the valve 207 and then lifts the valve 207 from its seat to provide open communication between the outlet 202 and the regulating chamber indicated at 216 above the piston 204. One or more ports 217 are formed in the lower portion of the boss 208 to provide direct communication between the passage 206 and the chamber 216. As the armature moves further and lifts the valve 207 the bar 214 comes into engagement with a flange or shoulder 218 on the boss 208 and lifts the boss and piston therewith to move it away from the valve seat 203. It can readily be understood that because of the lost motion resulting from the spacing between the bars 213 and 214 and the elements which they engage, there results a snap action in the opening of the valve 207 and in the lifting of the piston 204 for the seat 203. A stop 219 limits the upward movement of the piston.

The operation of the valve of FIG. 7 in a refrigeration system of the reversible type is essentially the same as that of valves for the systems shown in FIGS. 1 and 4. For purposes of preventing reverse flow of refrigerant under reversed pressure conditions, the port 206 is arranged to be closed by ball check valve indicated at 220, the ball being retained in the passage 206 by a pin 221 extending thereacross.

The improved reversible refrigerating system described above, together with the improved two-way check valves and selectively actuated valves make possible a simple, reliable and positively acting reversing control for refrigerating systems, particularly those such as employed in heat pumps for heating and cooling of zones to be air conditioned. The valves are of simple construction and are positive in actuation and require a minimum of service or attention during the operation of a refrigerating system in which they are installed.

While the invention has been disclosed in connection with particular arrangements of the control system and refrigerant circulating system, various modifications will occur to those skilled in the art, therefore it is not desired that the invention be limited to the particular arrangements and constructions illustrated and described and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.

I claim:

1. An automatic fluid flow control valve comprising a valve body having a cylinder therein, a valve piston mounted for reciprocating movement in said cylinder and positioned to divide said cylinder into a control chamber and fluid flow chamber, an inlet connection providing communication with said fluid flow chamber, an outlet connection having a valve seat positioned for engagement with said piston to prevent the passage of fluid from said inlet through said outlet connection, a bleed passage between said inlet and said control chamber, means providing communication between said control chamber and said outlet connection, a pilot valve for closing said communication means whereby upon opening of said pilot valve the fluid under pressure is released from said control chamber to afford opening of said valve when the pressure in said flow chamber exceeds the pressure in said outlet, and a check valve mounted in said communicating means to prevent reverse flow of fluid through said communicating means to said control chamber whereby said control valve is opened upon reverse flow conditions between said outlet and said inlet.

2. An automatic fluid flow control valve comprising a cylinder closed at its ends, a valve piston mounted for reciprocating movement in said cylinder and positioned r to divide said cylinder into a control chamber and a fluid flow chamber, means including an outlet connection having a valve seat positioned to be engaged by said valve piston for limiting the movement of said piston toward said fluid flow chamber and for preventing the flow of fluid through said outlet connection, means providing an inlet in communication with said fluid flow chamber in all positions of said piston, said valve piston having a bleed passage therein providing communication between said chambers to afford a flow of fluid from said inlet to said control chamber and a normally closed pilot valve port providing communication between said control chamber and said outlet connection, a pilot valve for closing said port, control means for opening said pilot valve whereby fluid may flow out of said control chamber to decrease the pressure therein and said valve piston is moved away from said seat by inlet pressure in said fluid flow chamber to open the passage from said inlet to said outlet and a check valve mounted in said piston for closing said port to prevent flow of fluid through said port to said control chamber.

3. An automatic fluid flow control valve comprising a cylinder closed at its ends, a valve piston mounted for reciprocating movement in said cylinder and positioned to divide said cylinder into a control chamber and a fluid flow chamber, means including an outlet connection having a valve seat positioned to be engaged by said valve piston for limiting the movement of said piston toward said fluid flow chamber and for preventing the flow of fluid through said outlet connection, means providing an inlet in communication with said fluid flow chamber in all positions of said piston, said valve piston having a bleed passage therein providing communication between said chambers to aiford a flow of fluid from said inlet to said control chamber and a normally closed pilot valve port providing communication between said control chamber and said outlet connection, a pilot valve for closing said port, control means for opening said pilot valve whereby fluid flow out of said control chamber to decrease the pressure therein and said valve piston is moved away from said seat by inlet pressure in said fluid flow chamber to open the passage from said inlet to said outlet and means for biasing said piston valve toward its position in engagement with said seat.

4. An automatic fluid flow control valve comprising a cylinder closed at its ends, a valve piston mounted for reciprocating movement in said cylinder and positioned to divide each cylinder into a control chamber and a fluid flow chamber, means including an outlet connection having a valve seat positioned to be engaged by said valve piston for limiting the movement of said piston toward said fluid flow chamber and for preventing the flow of fluid through said outlet connection, means providing an inlet in communication with said fluid flow chamber in all positions of said piston, said valve piston having a bleed passage therein providing communication between said chambers to afford a flow of fluid from said inlet to said control chamber and a normally closed pilot valve port providing communication between said control chamber and said outlet connection, a pilot valve for closing said port, control means for opening said pilot valve whereby fluid may flow out of said control chamber to decrease the pressure therein and said valve piston is moved away from said seat by inlet pressure in said fluid flow chamber to open the passage from said inlet to said outlet and said control means comprising an actuating member movable toward and away from the piston and engaging said pilot valve and constituting a guide therefor, said pilot valve and said actuating member being arranged for limited relative movement in the direction of movement of said actuator whereby said actuating member must move a predetermined distance away from said piston before picking up and opening said pilot valve.

5. An automatic fluid flow control valve comprising a cylinder closed at its ends, a valve piston mounted for reciprocating movement in said cylinder and positioned to divide said cylinder into a control chamber and a fluid flow chamber, means including an outlet connection having a valve seat positioned to be engaged by said valve piston for limiting the movement of said piston toward said fluid flow chamber and for preventing the flow of fluid through said outlet connection, means providing an inlet in communication with said fluid flow chamber in all positions to said piston, said valve piston having a bleed passage therein providing communication between said chambers to aflord a flow of fluid from said inlet to said control chamber and a normally closed pilot valve port providing communication between said control chamber and said outlet connection, a pilot valve for closing said port, control means for opening said pilot valve whereby fluid may flow out of said control chamber to decrease the pressure therein and said valve piston is moved away from said seat by inlet pressure in said fluid flow chamber to open the passage from said inlet to said outlet and said control means comprising a solenoid having a magnetic armature movable toward and away from said piston, and said pilot valve comprising a non-magnetic pin slidably mounted in said armature for limited relative movement in the direction of movement of the armature, said armature and said pilot valve having shoulders arranged to engage upon a predetermined relative movement of said pilot valve and armature and to open said pilot valve with snap action after energization of said solenoid.

6. An automatic fluid flow control valve comprising a cylinder closed at its ends, a valve piston mounted for reciprocating movement in said cylinder and positioned to divide said cylinder into a control chamber and a fluid flow chamber, means including an outlet connection having a valve seat positioned to be engaged by said valve piston for limiting the movement of said piston toward said fluid flow chamber and for preventing the flow of fluid through said outlet connection, means providing an inlet in communication with said fluid flow chamber in all positions of said piston, said valve piston having. a bleed passage therein providing communication between said chambers to afford a flow of fluid from said inlet to i moved away from said seat by inlet pressure in said fluid flow chamber to open the passage from said inlet to said outlet and said valve seat comprising an annular member and said piston having a shroud ring thereon spaced from and arranged to fit about said annular member when said valve is closed whereby an annular axially extending passage is provided between said outlet and said piston valve when they are near one another and on reverse flow of fluid from said outlet toward said inlet any tendency of said piston to remain near said valve seat because of low pressure due to the fluid velocity effect of radially flowing fluid is minimized.

7. An automatic fluid flow control valve comprising a cylindrical valve body, end closure members for saidbody, each of said members having a circular opening therein concentric with said body, an outlet tube concentric with said body and extending through the opening in one of said members and bonded to said member about the opening, said tube having an open end spaced from the other one of said members, an inlet connection arranged in communication with the space between said tube and said body, a valve piston mounted for reciprocation in said body between said tube and said other member for forming a control chamber on the side remote from said tube end for controlling the passage of fluid between said body and said tube, said tube having a valve seat about said open end arranged to engage said valve piston, said piston having a bleed passage therein between said control chamber and the space between said tube and said body, said valve piston having a pilot valve port therein providing communication between said control chamber and said tube, a pilot valve within said chamber positioned to close said port, actuating means for engaging said valve to open said port, and a housing for said actuating means arranged to close the opening in said other member.

8. An automatic fluid flow control valve according to claim 7 wherein said pilot valve port is in the center of said piston valve and said pilot valve comprises a nonmagnetic stem arranged for reciprocating movement along the center line of said body, and said actuating means comprises a magnetic armature engaging said pilot valve and movable toward and away from said piston within said housing, said housing comprising a non-magnetic tube closed at its outer end and concentric with said body and sealed to said other member about the opening therein, and a solenoid coil mounted about the outside of said housing for moving said armature.

9. An automatic fluid flow control valve according to claim 7 including a shroud ring on said piston positioned to fit about the end of said tube in the closed position of said valve, said ring being of slightly greater internal diameter than the external diameter of said tube whereby a restricted substantially axial passage is provided between said ring and said tube, said ring being substantially spaced from said tube in the open position of said valve.

10. In a reversible refrigerating system having first and second heat transfer units and a refrigerant compressor connected in a refrigerant circuit, said compressor having intake and discharge ports, a flow restricting element in said circuit between said units, and alternatively positioned connecting means for connecting the discharge port of said compressor to either of said units and the intakeport of said compressor to the other unit, comprising a first pair of conduits connecting said first and second units to said intake port and a second pair of conduits connecting said first and second units to said discharge port, the improvement comprising a refrigerant fluid flow control valve system including a two-way check valve between the conduits of one of said pairs and one of said ports, a pair of selectively and alternatively actuatable independent valves one in each of the conduits of the other of said pairs of conduits, each of said independent valves constituting a check valve when the other valve of the pair is actuated providing an unrestricted one-way passage between the inlet port and the discharge port of said compressor, said two-way check valve being positioned and arranged to close automatically its passage to the one of said units connected to said one port of said compressor upon operation of the selected one of said independent valves.

11. In a reversible refrigerating system having first and second heat transfer units and a refrigerant compressor connected in a closed refrigerant circuit, said compressor having intake and discharge ports, a flow restricting element in said circuit between said units, and alternatively positioned connecting means for connecting the discharge port of said compressor to either of said units and the intake port of said compressor to the other unit comprising a first pair of conduits connecting said first and second units respectively to said intake port and a second pair of conduits connecting said first and second units to said discharge port, the improvement comprising a refrigerant fluid flow control valve system including a twoway check valve between the conduits of one of said pairs and one of said ports, a pair of independent solenoid controlled valves one in each of the conduits of the other of said pairs of conduits, each of said solenoid controlled valves constituting a check valve when its respective solenoid is de-energized, said two-way check valve being positioned and arranged to close automatically its passage to the one of said units connected to the other port of said compressor upon operation of the valve actuated by said other solenoid, said two-way check valve and one of said solenoid controlled valves providing an unrestricted oneway passage between the inlet port and the discharge port of said compressor.

12. In a reversible refrigerating system or the like of the type comprising a high pressure fluid discharge port and a low pressure fluid inlet port and a pair of heat exchangers connected to operate as the condenser and evaporator of the system and alternatively to operate as the evaporator and condenser, respectively, a fluid flow control for selectively connecting the heat exchangers in their two alternative positions comprising selectively actuatable valve means for connecting one port to either one of the heat exchangers and for affording upon its actuation a free and open one-way communication between the heat exchangers and between the said low pressure inlet port and the high pressure discharge port, and a second valve means effective upon operation of the first and dependent upon the change in pressure difference resulting therefrom for completing the connection of the other port of the system to the other one of the heat exchangers.

13. In a reversible refrigerating system or the like of the type having a high pressure fluid supply port and a low pressure fluid inlet port and a pair of heat exchangers connected to operate as the condenser and evaporator of the system and alternatively to operate as the evaporator and condenser, respectively, the improvement comprising: a fluid flow control for selectively connecting the heat exchangers in their two alternative positions comprising a first valve means movable to either of two positions for selectively connecting either of the heat exchangers to one of the ports of the system, said valve means affording free and open communication between the heat exchangers upon movement of said valve means from one of said positions toward the other to unload said system, and a second valve means movable into either of two positions for connecting the other port of the system alternatively to either heat exchanger, said second means including means responsive to unloading of the system and subsequent pressure differences therein for automatically connecting said other port to the other of the heat exchangers, said highpressure fluid supply port and the low pressure fluid inlet port being in direct interconnection during the unloading of the system.

14. A fluid flow control valve system for selectively determining the direction of flow of refrigerant through a reversible refrigerating system of the type including a refrigerant compressor having intake and discharge ports and two heat exchange units connected by a pressure reducing device and adapted to operate alternatively as the evaporator and condenser of the system, said control comprising a two position valve for connecting a first compressor port alternatively to the two heat exchangers of the system, a pair of separately movable valves for connecting a second compressor port alternatively to either of the two heat exchangers, means affording free and open one-way communication between the two heat exchangers through said movable valves to shift the connection of the second port from one exchanger to the other and providing direct interconnection between the two ports of the compressor during said shift to unload said compressor, and means dependent upon the build up of pressure difference in the opposite direction between the two exchangers after unloading for shifting said two position valve to its opposite position.

15. A reversible refrigerating system comprising:

(1) a compressor having an intake port and a discharge port, and a combination comprising two heat exchangers connected in a refrigerant circuit with the compressor wherein the heat exchangers are interconnected in a condenser-to-evaporator sequence during flow of the refrigerant, said circuit including a first pair of conduits connecting the heat exchangers to said intake port and a second pair of conduits connecting the heat exchangers to said discharge port; (II) means for controlling the direction of the flow of the refrigerant through the interconnected heat exchangers;

said control means comprising a combination of valves comprising a first check valve and a second check valve, one of said check valves being in one of the conduits of one of said pair and being normally open, the other check valve being in the other of the conduits of the same pair and being normally closed, and a two way-check-three-way valve between the conduits of the other pair, and (III) direction-change means for changing the direction of refrigerant fluid through the heat exchanger comprising means which automatically changes said normal position of one of said check valves while said normal position of the other of said check valves remains unchanged, said automatic change effecting a division of the refrigerant circuit into two separate loops, the first of said loops comprising interconnection of the intake and discharge ports of the compressor, thereby forming a refrigerant sub-circuit from which the heat exchangers are excluded, and the second of said loops comprising the balance of the re-- frigerant circuit from which the compressor is excluded,

said division into two loops providing for equalization of pressure in the second loop and operation of the compressor without pressure thereon,

followed by a shifting in the operative position of the two-way-check-three-Way valve, and a change in the position of the check valve which has remained unchanged, whereby said shift and last-mentioned change terminate the existence of the two loops and establish a single refrigerant circuit of reversed direction.

16. A reversible refrigeration system having high and low pressure sides comprising: a compressor; a first heat transfer unit; a second heat transfer unit and a restricting means connecting the units; reversing means for passing refrigerant fluid from the compressor output through the first unit, the restriction means and the second unit for operation in a first mode, and for rerouting the fluid to pass from the compressor output through the second unit, the restriction means and then the first unit for operation in a second mode, said reversing means including a plurality of valve members and a plurality of conduits external of the compressor for providing a direct fluid passage between the compressor output and intake at the time of reversal, said reversing means further including control and delay means for said plurality of valve members operative while the compressor is running for maintaining said fluid passage open for a length of time sufficient to substantially unload the compressor and to substantially equalize the pressure differences between the high and low sides of the system, said control means being operative to close said fluid passage before the fluid is rerouted for flow in the opposite mode.

17. A reversible refrigeration system having high and low sides comprising: a compressor; a first heat transfer unit; a second heat transfer unit; restricting means connecting the units; a first valve element disposed in an open-valve position and passing refrigerant fluid from the compressor output through the first unit, the restriction means, the second unit and to the compressor inlet for operation in a first mode; a second valveelement disposed in a closed-valve position and operable for passing refrigerant fluid from the compressor output through the second unit, the restriction means, then the first unit to the compressor inlet for operation in a second mode when said second valve element is in an open-valve position and when said first valve element is in its closed-valve position; and reversing means for providing a direct fluid passage by way of said valve elements between the compressor output and intake while the compressor is running to substantially equalize the pressure differences between the high and low sides of the system and between the intake and output of the compressor and for then rerouting the refrigerant fluid by way of the second valve element to said heat transfer units in the opposite mode, said reversing means including actuating means for moving said first valve element toward its closed-valve position and said second valve element toward its openvalve position, said reversing means further including control means operable upon operation of said actuating means and responsive to pressure differences within the system while said compressor is running for rapidly moving said second valve element to its open-valve position and for delaying arrival of said first valve element at its closed-valve position until pressure differences between high and low sides of the system and between the compressor intake and output have been substantially equalized by fluid flow through a direct fluid passage between said intake and output by way of said first and second valve elements whereupon said first valve element moves to its closed-valve position thereby reversing the direction of fluid flow through said heat transfer units.

References Cited by the Examiner UNITED STATES PATENTS 2,558,938 7/51 Dillman 62-160 2,654,227 10/53 Muffly 62-160 2,774,223 12/56 Mufily 62-71 2,795,112 6/57 Mufliy 6216O 2,875,780 3/59 Martin 62324 WILLIAM J. WYE, Primary Examiner.

ROBERT A. OLEARY, Examiner. 

1. AN AUTOMATIC FLUID FLOW CONTROL VALVE COMPRISING A VALVE BODY HAVING A CYLINDER THEREIN, A VALVE PISTON MOUNTED FOR RECIPROCATING MOVEMENT IN SAID CYLINDER AND POSITIONED TO DIVIDE SAID CYLINDER INTO A CONTROL CHAMBER AND FLUID FLOW CHAMBER, AN INLET CONNECTION PROVIDING COMMUNICATION WITH SAID FLUID FLOW CHAMBER, AN OUTLET CONNECTION HAVING A VALVE SEAT POSITIONED FOR ENGAGEMENT WITH SAID PISTON TO PREVENT THE PASSAGE OF FLUID FROM SAID INLET THROUGH SAID OUTLET CONNECTION, A BLEED PASSAGE BETWEEN SAID INLET AND SAID CONTROL CHAMBER, MEANS PROVIDING COMMUNICATION BETWEEN SAID CONTROL CHAMBER AND SAID OUTLET CONNECTION, A PILOT VALVE FOR CLOSING SAID COMMUNICATION MEANS WHEREBY UPON OPENING OF SAID PILOT VALVE THE FLUID UNDER PRESSURE IS RELEASED FROM SAID CONTROL CHAMBER TO AFFORD OPENING OF SAID VALVE WHEN THE PRESSURE IN SAID FLOW CHAMBER EXCEEDS THE PRESSURE IN SAID OUTLET, AND A CHECK VALVE MOUNTED IN SAID COMMUNICATING MEANS TO PREVENT REVERSE FLOW OF FLUID THROUGH SAID COMMUNICATING MEANS TO SAID CONTROL CHAMBER WHEREBY SAID CONTROL VALVE IS OPENED UPON REVERSE FLOW CONDITIONS BETWEEN SAID OUTLET AND SAID INLET. 